Students learn that a permutation is an arrangement of objects in which the order is important. For example, the permutation AB is different than the permutation BA. Students are then asked to solve word problems involving permutations. For example: Find the number of different ways 6 books can be arranged on a shelf. Note that the number of permutations can be found by multiplying the number of choices for the 1st position (6 books) times the number of choices for the second position (5 books), and so on. So the number of permutations is 6 x 5 x 4 x 3 x 2 x 1, or 720. In other words, there are 720 different ways 6 books can be arranged on a shelf.